I thought that censoring speech in privately owned public spaces was fine. It's only when a government censors speech that the first amendment kicks in.

I do, as it happens, believe it is a problem that Twitter censors so much speech without 'legitimacy'. Not because they censor the wrong things, but because their censorship without legitimacy fuels a persecution complex.

This is mostly a problem because Twitter is so big. And I don't think starting alternative Twitters (like truth social) is a good solution, mostly because it partitions the conversation even more.